Utility companies have historically used the method of reading meters and rendering bills as a means for collecting for electric, gas, and water service after it has been used by the customer. More recently, prepayment metering systems have been proposed in the prior art as a technology for overcoming some of the shortcomings of the traditional billing system. These prepayment systems were designed so that the purchase of a supply of electricity, gas, or water is made at a central station such as the gas or electric utility office, and the information regarding the amount of the purchase is then communicated to the customer site where the utilities are consumed. At the customer site a metering device is installed which is designed to receive the prepayment communication information and credit the user with the amount purchased at the central site. These types of proposed prepayment metering systems will reduce the overall cost of utility distribution by reducing or eliminating meter reading expenses, bad debt collection, account transfer expenses and credit department expenses, while at the same time providing a greater awareness on the consumer's part as to his or her consumption habits.
An example of a prior art utility company device of the aforementioned type is described in U.S. Pat. No. 4,731,575 to Joseph W. Sloan, which describes a microprocessor-controlled utility device which receives payment information on a mag-stripe card and allows the utility service to continue so long as the pre-purchased amount has not been exhausted. This device includes a display that the customer can use to monitor the utility usage at the customer site, including present rate of use, amount used the previous day, and the amount remaining.
One characteristic inherent in the prepayment for utility service is the possibility of service being interrupted because of a failure of the customer to make a timely purchase before the supply is exhausted. Therefore, in order for a prepayment system to be generally acceptable to the majority of customers, it is necessary that the customer be able to make additional purchases at any time of the day or night from one or more convenient stations located nearby. These remote purchase stations may be attended or unattended, but are most cost-effective if unattended.
A primary concern of prepayment metering systems is a communications method which cannot be breached by unauthorized personnel for the purpose of obtaining or continuing the utility service without proper payment. An example of an effective prior art communications security method is the sequential password described in the aforementioned U.S. Pat. No. 4,731,575. However, that system does not provide the flexibility and customer convenience required for operating large numbers of card purchase stations serving very large numbers of utility customers over a wide geographic area.
Another concern of prepayment is the opportunity for the customer to pre-purchase a very large quantity of utility service at the present lower rate prior to an announced increase in rates in order to continue to use service for an extended period of time at the lower rate. Furthermore, with the elimination of monthly meter reading, the opportunity for utility personnel to observe possible tampering or meter failure is greatly reduced.
The present invention overcomes these and other shortcomings of the prior art utility prepayment systems by providing a simple, low-cost communications and control system based primarily on existing and off-the-shelf components and by expanding the sequential password scheme such that the customer premise equipment will recognize and accept value and other information encoded on cards issued from several different purchase locations. The present invention uses an encoding scheme and relies on other mechanical and monitoring devices to bolster the overall security and reliability of the system.